(Received 19 January 2011;accepted 20 January 2011;online 26 January 2011)

The least-squares planes defined by the aromatic moieties in the title aniline derivative, C13H13NS, are nearly perpendicular to each other, forming a dihedral angle of 87.80 (7)°. Apart from a weak intramolecular N—H⋯S hydrogen bond, a co-operative set of N—H⋯N hydrogen bonds present in the crystal structure leads to the formation of tetra­meric units.

2-(p-Tolylthio)benzenamine is a derivative of aniline bearing a para-methylbenzene sulfide moiety in a position ortho to its amino group. Given its N,S set of donor atoms, it can act as a monodentate via either donor or as a bidentate ligand forming a five-membered chelate ring. The possibility to coordinate it as a purely neutral or, upon deprotonation, as an anionic ligand adds to its versatility. In our continued efforts to elucidate the coordination behaviour of nitrogen- and sulfur-containing ligands, it seemed of interest to determine the structure of the free ligand to enable comparative studies with related structures (Yuan et al., 2008; Sellmann et al., 1999; Heinisch et al., 1999).

The least-squares planes defined by the two aromatic moieties in the molecule are orientated nearly perpendicular to each other; they enclose an angle of 87.80 (7)°. The C2–S1–C7 angle is 103.21 (12) ° (Fig. 1).

In the crystal structure, two different sets of hydrogen bonds can be observed, Table 1. While one of the hydrogen atoms of the amino group forms an intramolecular hydrogen bond to the sulfur atom, the remaining hydrogen atom of the NH2 group participates in a cooperative system of hydrogen bonds. The latter give rise to the formation of tetrameric units. In terms of graph-set analysis (Etter et al., 1990; Bernstein et al., 1995), the descriptor for the intramolecular interaction is S(5) while the cooperative system of hydrogen bonds necessitates a C11(2) descriptor. The tetramer has a hydrophilic core which is shielded by the lipophilic parts of the molecules (Fig. 2). The closest distance between two aromatic systems is 4.0711 (16) Å. The molecular packing of the compound is shown in Fig. 3.

H-atoms were placed in calculated positions (C—H 0.95 Å for aromatic C-atoms, C—H 0.98 Å for the methyl group) and were included in the refinement in the riding model approximation, with U(H) set to 1.2Ueq(C) for aromatic carbon atoms and 1.5Ueq(C) for the methyl group. The H-atoms of the amino group were located from a difference Fourier map and refined with U(H) set to 1.5Ueq(N).

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